Electronic film editing system using both film and videotape format

ABSTRACT

A system for generating a digital representation of a video signal comprised of a sequence of video frames which each include two video fields of a duration such that the video plays at a first prespecified rate of frames per second. The sequence of video frames includes a prespecified number of redundant video fields. Redundant video fields in the video frame sequence are identified by a video processor, and the video frame sequence is digitized by an analog to digital converter, excluding the identified redundant video fields. The digitized video frames are then compressed by a video compressor to generate a digital representation of the video signal which plays at a second prespecified rate of frames per second.

BACKGROUND OF THE INVENTION

[0001] This invention relates to techniques for electronically editingfilm.

[0002] Film video and audio source material is frequently editeddigitally using a computer system, such as the Avid/1 Media Composerfrom Avid Technology, Inc., of Tewksbury, Mass., which generates adigital representation of a source film, allowing a film editor to editthe digital version, rather than the film source itself. This editingtechnique provides great precision and flexibility in the editingprocess, and is thus gaining popularity over the old style of filmediting using a flatbed editor.

[0003] The Avid/1 Media Composer accepts a videotape version of a sourcefilm, created by transferring the film to videotape using the so-calledtelecine process, and digitizes the videotape version for editing viamanipulation by computer. The operation of the Media Composer isdescribed more fully in copending application U.S. Ser. No. 07/866,829,filed Apr. 10, 1992, and entitled Improved Media Composer. The teachingsof that application are incorporated herein by reference. Editing of thedigitized film version is performed on the Media Composer computer usingCRT monitors for displaying the digitized videotape, with the editdetails being based on videotape timecode specifications. Once editingis complete, the Media Composer creates an edited videotape and acorresponding edit decision list (EDL) which documents the videotapetimecode specification details of the edited videotape. The film editoruses this EDL to specify a cut and assemble list for editing the sourcefilm. While providing many advantages over the old style flatbed filmediting technique, this electronic editing technique is found to becumbersome for some film editors who are unaccustomed to videotapetimecode specifications.

SUMMARY OF THE INVENTION

[0004] In general, in one aspect, the invention provides a system forgenerating a digital representation of a video signal comprised of asequence of video frames which each include two video fields of aduration such that the video plays at a first prespecified rate offrames per second The sequence of video frames includes a prespecifiednumber of redundant video fields. In the invention, redundant videofields in the video frame sequence are identified by a video processor,and the video frame sequence is digitized by an analog to digitalconvertor, excluding the identified redundant video fields. Thedigitized video frames are then compressed by a video compressor togenerate a digital representation of the video signal which plays at asecond prespecified rate of frames per second.

[0005] In preferred embodiments, the invention further provides forstoring the digitized representation of the video signal on a digitalstorage apparatus. The redundant video fields are identified byassigning a capture mask value to each video field in the video framesequence, the capture mask value of a field being a “0” if the field isredundant, and the capture mask value of a field being a “1” for allother video fields. A video frame grabber processes the video framesequence based on the capture mask values to exclude the identifiedredundant video frames from being digitized. The video compressorcompresses the video frames based on JPEG video compression.

[0006] In other preferred embodiments, the first prespecified video playrate is 29.97 frames per second and the second prespecified digitalvideo play rate is 24 frames per second. The rate of the analog videosignal is increased from 29.97 frames per second to 30 frames per secondbefore the step of digitizing the video frame sequence. In furtherpreferred embodiments, the analog video signal is a video representationof film shot at 24 frames per second, and the digital video play rate of24 frames per second corresponds to the 24 frames per second filmshooting rate. The analog video signal is a representation of film thatis transferred to the video representation using a telecine apparatus.

[0007] In general, in another aspect, the invention provides anelectronic editing system for digitally editing film shot at a firstprespecified rate and converted to an analog video representation at asecond prespecified rate. The editing system includes analog to digitalconverting circuitry for accepting the analog video representation ofthe film, adjusting the rate of the analog video such that the ratecorresponds to the first prespecified rate at which the film was shot,and digitizing the adjusted analog video to generate a correspondingdigital representation of the film. Further included is a digitalstorage apparatus for storing the digital representation of the film,and computing apparatus for processing the stored digital representationof the film to electronically edit the film and correspondingly edit thestored digital representation of the film.

[0008] In preferred embodiments, the system further includes digital toanalog converting circuitry for converting the edited digitalrepresentation of the film to an analog video representation of thefilm, adjusting the rate of the analog video from the first prespecifiedrate to the second prespecified video rate, and outputting the adjustedanalog video. Preferably, the analog video representation of the filmaccepted by the analog to digital converting circuity is an NTSCvideotape. The apparatus for storing the digital representation of thefilm also stores a digitized version of a film transfer logcorresponding to the digital representation of the film. The systemincludes display apparatus for displaying the digitized version of thefilm as the film is electronically edited and displaying a metric fortracking the location of a segment of the film as the segment isdisplayed, the metric being based on either film footage code or videotime code, as specified by the system user.

[0009] The electronic editing system of the invention allows users toprovide the system with film formatted on standard videotapes, NTSCtapes, for example, and yet allows the video to be digitally edited asif it were film, i.e., running at film speed, as is preferred by mostfilm editors. By reformatting the analog video as it is digitized, thesystem provides the ability to electronically edit film based on thesame metric used in conventional film editing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a schematic diagram of the electronic editing system ofthe invention.

[0011]FIG. 2 is a diagram of the telecine film-tape transfer pulldownscheme.

[0012]FIG. 3 is a schematic diagram of the telecine film-tape transfersystem.

[0013]FIG. 4 is an Evertz Film Transfer Log produced by the telecinetransfer system and processed by the editing system of the invention.

[0014]FIG. 5 is an illustration of a video screen showing the electronicbin generated by the editing system of the invention.

[0015]FIG. 6 is a diagram of the scheme employed by the editing systemin digitizing a video input to the system.

[0016]FIG. 7 is an illustration of a video screen showing the digitizedvideo to be edited on the electronic editing system of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] Referring to FIG. 1, there is shown the electronic editing systemof the invention 10, including two CRT displays 12, 14 for displayingdigitized film during an editing session, and an audio output device 16,for example, a pair of speakers, for playing digitized audio during anediting session. The displays 12, 14 and audio output 16 are allcontrolled by a computer 18. Preferably, the computer is a Macintosh™II_(ci), II_(fx), Quadra 900, or Quadra 950 all of which are availablefrom Apple Computer, Inc., of Cupertino, Calif. The system includes avideo tape recorder (VTR) 20 for accepting an electronic version of filmfootage, which is preprocessed and digitized by a video analog todigital converter (A/D) 26. A timing circuit 28 controls the speed ofthe video being digitized, as described below. A video compressor 30 isconnected to the video A/D for compressing the electronic image data tobe manipulated by the computer 18. An audio A/D 22 and audio processor24 process audio information from the electronic version of film footagein parallel with the video processing. Disc storage 32 communicates withthe computer to provide memory storage for digitized electronic imagedata. This disc storage may be optical, magnetic, or some other suitablemedia. The editing system is user-interfaced via a keyboard 34, or someother suitable user control interface.

[0018] In operation, video and audio source material from a film whichhas been transferred to a videotape is received by the system via thevideo tape recorder 20, and is preprocessed and digitized by the audioAD 22, audio processor 24, video A/D 26, and video compressor 30, beforebeing stored in the disc storage 32. The computer is programmed todisplay the digitized source video on a first of the CRTs 12 and playthe accompanying digitized source audio on the audio output 16.Typically source material is displayed in one window 36 of the first CRT12 and edited material is displayed in a second window 38 of that CRT.Control functions, edit update information, and commands input from thekeyboard 32 are typically displayed on the second system CRT 14.

[0019] Once a film is input to the system, a film editor mayelectronically edit the film using the keyboard to make edit decisioncommands. As will be explained in detail below, the electronic editingsystem provides the film editor with great flexibility, in that thevideo displayed on the system CRT 12 may be measured and controlled ineither the domain of film footage or the domain of videotape time code.This flexibility provides many advantages over prior electronic editingsystems. At the end of an editing session, the electronic editing systemprovides the film editor with an edited videotape and both tape and filmedit command lists for effecting the edits from the session on film orvideotape.

[0020] As explained above, the electronic editing system 10 requires avideotape version of a film for electronic manipulation of that film.Such a tape is preferably generated by a standard film-tape transferprocess, the telecine process, which preferably uses the Time LogicController™ telecine (TLC), a device that converts film into a videosignal, then records the signal on videotape. A TLC controls thefilm-tape transfer more precisely than non-TLC systems. In addition, itoutputs a report, described below, that includes video formatspecifications, i.e., timecode, edge number, audio timecode, scene, andtake for each reference frame in each tape, thereby eliminating the needto search through the video or film footage manually to find the datarequired for creating a log of video playing particulars. Other telecinesystems may be used, however, depending on particular applications.

[0021] Transfer from film to tape is complicated by the fact that filmand video play at different rates—film plays at 24 frames per second(fps), whereas PAL video plays at 25 fps and NTSC (National TelevisionStandards Committee) video plays at 29.97 fps. If the film is shot atthe standard rate of 24 fps and then transferred to 29.97 fps NTSCvideo, the difference between the film and video play rates is large(and typically unacceptable). As a result, the film speed must beadjusted to accommodate the fractional tape speed, and some film framesmust be duplicated during the transfer so that both versions have thesame duration. However, if the film is shot at 29.97 fps, thentransferring the footage to NTSC video is simple. Each film frame isthen transferred directly to a video frame, as there are the same numberof film and video frames per second.

[0022] Considering the most common case, in which 24 fps film is to betransferred to 29.97 fps NTSC videotape, the telecine process mustprovide both a scheme for slowing the film and a frame duplicationscheme. The film is slowed down by the telecine apparatus by 0.1% of thenormal film speed, to 23.976 fps, so that when the transfer is made, thetape runs at 29.97 fps, rather than 30 fps. To illustrate the frameduplication scheme, in the simplest case, and disregarding the filmslowdown requirement, one second of film would be transferred to onesecond of video. The one second of film would include 24 frames of filmfootage, but the corresponding one second of video would require 30frames of footage. To accommodate this discrepancy, the telecine processduplicates one film frame out of every four as the film is transferredto tape, so that for each second of film footage, the correspondingsecond of tape includes six extra frames.

[0023] Each video frame generated by the telecine process is actually acomposite of two video fields: an odd field, which is a scan of the oddlines on a video screen, and an even field, which is a scan of the evenlines. A video field consists of 262 ½ scan lines, or passes of anelectron beam across a video screen. To create a fill video framecomprised of 525 scan Lines, an odd field, or scan of the odd lines, isfollowed by an even field, or scan of the even lines. Thus, when aduplicate video frame is generated and added in the telecine process,duplicate video fields are actually created. During play of theresulting tape, each two video fields are interlaced to make a singleframe by scanning of the odd lines (field one) followed by scanning ofthe even lines (field two) to create a complete frame of NTSC video.

[0024] There are two possible systems for creating duplicate videofields in the telecine process, those systems being known as 2-3pulldown and 3-2 pulldown. The result of the 2-3 pulldown process isschematically illustrated in FIG. 2. In a film-tape transfer using 2-3pulldown, the first film frame (A in FIG. 2) is transferred to 2 videofields AA of the first video frame; the next film frame B is transferredto 3 video fields BBB, or one and one half video frames, film frame C istransferred to two video fields CC, and so on. This 2-3 pulldownsequence is also referred to as a SMPTE-A transfer. In a 3-2 pulldowntransfer process, this sequence of duplication is reversed; the firstfilm frame A would be mapped to 3 video fields, the next film frame Bwould be mapped to 2 video fields, and so on. This 3-2 pulldown sequenceis also referred to as a SMPTE-B transfer. In either case, 4 frames offilm are converted into 10 video fields, or 5 frames of video footage.When a 2-3 pulldown sequence is used, an A, B, C, D sequence in theoriginal film footage creates an AA, BB, BC, CD, DD sequence of fieldsin the video footage, as shown in FIG. 2. The telecine process slowsdown the film before the frame transfer and duplication process, so thatthe generated video frames run at 29.97 fps.

[0025] Referring to FIG. 3, as discussed above, the telecine 36 producesa video signal from the film; the video is generated to run at 29.97 fpsand includes redundant film frames from the pulldown scheme. NAGRA™audio timecode is the typical and preferable system used with films fortracking the film to its corresponding audiotape. During the telecineprocess, a corresponding audio track 38 is generated based on the NAGRA™and is slowed down by 0.1% so that it is synchronized to the slowed filmspeed. The sound from the film audiotrack is provided at 60 Hz; a timingreference 40 at 59.94 Hz slows the audio down as required. Thus, thetelecine process provides, for recordation on a videotape 48 via avideotape recorder 20, a video signal (V in the figure), correspondingaudio tracks, A_(i)-A_(n), and the audio timecode (audio TC).

[0026] A further film-tape correspondence is generated by the telecineprocess. This is required because, in addition to the difference betweenfilm and video play rates, the two media employ different systems formeasuring and locating footage. Film is measured in feet and frames.Specific footage is located using edge numbers, also called edge code orlatent edge numbers, which are burned into the film For example, Kodakfilm provides Keykode™ on the film to track footage. The numbers appearonce every 16 frames, or once every foot, on 35 mm film. The numbersappear once every 20 frames, or every half foot, on 16 mm film. Notethat 35 mm film has 16 frames per foot, while 16 mm film has 40 framesper foot. Each edge number includes a code for the film manufacturer andthe film type, the reel, and a footage counter. Frames between markededge numbers are identified using edge code numbers and frame offsets.The frame offset represents the frame's distance from the preceding edgenumber.

[0027] Videotape footage is tracked and measured using a time-basesystem Time code is applied to the videotape and is read by a time codereader. The time code itself is represented using an 8-digit format:XX:XX:XX:XX—hours:minutes:seconds:frames. For example, a frame occurringat 11 minutes, 27 seconds, and 19 frames into the tape would berepresented as 00:11:27:19.

[0028] It is preferable that during the telecine conversion, a log,called a Film Transfer Log (FTL), is created that makes a correspondencebetween the film length-base and the video time-base. The FTL documentsthe relationship between one videotape and the raw film footage used tocreate that tape, using so-called sync points. A sync point is adistinctive frame located at the beginning of a section of film, say, aclip, or scene, which has been transferred to a tape. The followinginformation documents a sync point: edge number of the sync point in thefilm footage, time code of the same frame in the video footage, the typeof pulldown sequence used in the transfer, i.e., 2-3 pulldown or 3-2pulldown, and the pulldown mode of the video frame, i.e., which of theA, B, C, and D frames in each film five-frame series corresponds to thesync point frame.

[0029] As shown in FIG. 3, an Evertz 4015 processor accepts the videosignal from the telecine and the audio TC corresponding to theaudiotrack and produces a timecode based on a synchronization of theaudio and video. Then an Evertz PC 44 produces an Evertz FTL 46 whichincludes the sync point information defined above.

[0030]FIG. 4 illustrates a typical Evertz FTL 46. Each column of thelog, specified with a unique Record #, corresponds to one clip, or sceneon the video. Of particular importance in this log is the VideoTape TimeCode In (VTTC IN) column 50 and VideoTape Time Code Out (VTTC OUT)column 52. For each scene, these columns note the video time code of thescene start and finish. In a corresponding manner, the Keyin column 54and Keyout column 56 note the same points in film footage and frames.The Pullin column 58 and Pullout column 60 specify which of the A, B, C,or D frames in the pulldown sequence correspond to the frame at thestart of the scene and the close of the scene. Thus, the FTL gives scenesync information that corresponds to both the video domain and the filmdomain.

[0031] The electronic editing system of the invention accepts avideotape produced by the telecine process and an Evertz FTL, stored on,for example, a floppy disk. When the FT data on the disk is entered intothe system, the system creates a corresponding bin in memory, stored onthe system disc, in analogy to a film bin, in which film clips arestored for editing. The electronic bin contains all fields necessary forfilm editing, all comments, and all descriptions. The particulars of thebin are displayed for the user on one of the system's CRTs. FIG. 5illustrates the display of the bin. It corresponds directly to theEvertz FTL. The “Start” and “End” columns of the bin correspond to theVideoTape Time Code In and VideoTape Time Code Out columns of the FTLThe “KN Start” and “KN End” columns of the bin correspond to the Keyinand Keyout columns of the FTL. During an editing session, the bin keepstrack of the editing changes in both the video time-base and the filmfootage-base, as described below. Thus, the bin provides the film editorwith the flexibility of keeping track of edits in either of the metrics.

[0032] Referring again to FIG. 1, when the electronic editing system 10is provided with a videotape at the start of a film editing session, thevideotape recorder 20 provides to the computer 18 the video and audiosignals corresponding to the bin. The video signal is first processed bya video A/D coprocessor 26, such as the NuVista board made by TrueVisionof Indianapolis, Ind. A suitable video coprocessor includes a videoframe grabber which converts analog video information into digitalinformation. The video coprocessor has a memory which is configuredusing a coprocessor such as the TI34010 made by Texas Instruments, toprovide an output data path to feed to the video compression circuitry,such as JPEG circuity, available as chip CL550B from C-Cube of Milpitas,Calif. Such a configuration can be performed using techniques known inthe art. A timing circuit 28 controls the speed of the video signal asit is processed.

[0033] In operation, the video A/D 26 processes the video signal toreformat the signal so that the video represented by the signalcorresponds to film speed, rather than videotape speed. The reformattedsignal is then digitized, compressed, and stored in the computer forelectronic film editing. This reformatting process allows users toprovide the editing system with standard videotapes, in NTSC format, yetallows the video to be edited as if it were film, i.e., running at filmspeed, as is preferred by most film editors.

[0034] Referring also to FIG. 6, in this reformatting process, the speedof the video from the videotape is increased from 29.97 fps to 30 fps,as commanded by the timing circuitry 28 (FIG. 1). Then the fields of thevideo are scanned by the system, and based on the pulldown sequence andpulldown mode specified for each scene by the bin, the redundant videofields added by the telecine process are noted, and then ignored, whilethe other, nonredundant, fields are digitized and compressed intodigital frames. More specifically, a so-called “capture mask” is createdfor the sequence of video fields; those fields which are redundant areassigned a capture value of “0” while all other fields are assigned acapture value of “1”. The system coprocessor reads the entire capturemask and only captures those analog video fields corresponding to a “1”capture value, ignoring all other fields. In this way, the original filmframe sequence is reconstructed from the video frame sequence. Once allthe nonredundant fields are captured, the fields are batch digitized andcompressed to produce digitized frames.

[0035] Assuming the use of the 2-3 pulldown scheme, as discussed above,in the capture process, the first two analog video fields (AA in FIG. 6)would each be assigned a capture value of “1”, and thus would bedesignated as the first digital frame; the next two analog video fieldsBB would also each be assigned a capture value of “1”, and be designatedas the second digital frame; but the fifth analog video field B, whichis redundant, would be assigned a capture value of “0”, and would beignored, and so on. Thus, this process removes the redundant 6 framesadded by the telecine process for each film second from the video,thereby producing a digitized representation which corresponds directlyto the 24 fps film from which the video was made. This process ispossible for either the 2-3 or 3-2 pulldown scheme because the binspecifies the information necessary to distinguish between the twoschemes, and the starting frame (i.e., A, B, C, or D) of either sequenceis given for each scene.

[0036] Appendix A of this application consists of an example of assemblylanguage code for the MacIntosh™ computer and the TI 34010 coprocessorfor performing the reformatting process. This code is copyrighted, andall copyrights are reserved.

[0037] Referring again to FIG. 1, an audio A/D 22 accepts audio from avideotape input to the editing system, and like the video A/D 26,increases the audio speed back to 100%, based on the command of thetiming circuitry 28. The audio is digitized and then processed by theaudio processor 24, to provide digitized audio corresponding to thereformatted and digitized video. At the completion of this digitizationprocess, the editing system has a complete digital representation of thesource film in film format, i.e., 24 fps, and has created a bin withboth film footage and video timecode information corresponding to thedigital representation, so that electronic editing in either time-baseor footage-base may begin.

[0038] There are traditionally three different types of film productionsthat shoot on film, each type having different requirements of theelectronic editing system. The first film production type, commercials,typically involves shooting on 35 mm film, transferring the film to avideotape version using the telecine process, editing the video based onthe NTSC standard, and never editing the actual film footage, which isnot again needed after the film is transferred to video. Thus, theelectronic editing is here preferably based on video timecodespecifications, not film footage specifications, and an NTSC video ispreferably produced at the end of the edit process. The electroniccommercial edit should also preferably provide an edit decision list(EDL) that refers back to the video; the edited version of this video istypically what is actually played as the final commercial.

[0039] The second production type, episodic film, involves shooting oneither 35 or 16 mm film, and producing an NTSC videotape version andadditionally, an (optional) edited film version for distribution inmarkets such as HDTV (High Definition Television) or foreign countries.To produce the edited film footage for the film version, the film istransferred to videotape using the telecine process, and electronicediting of the film is here preferably accomplished based on filmfootage, and should produce a cutlist, based on film footagespecifications, from which the original film is cut and transferred tothe NTSC format. To produce a video version, the videotape is thenpreferably edited based on video timecode specifications to produce anEDL for creating an edited video version.

[0040] The third film production type, feature film, typically involvesshooting on 35 mm film, and produces a final film product; thuselectronic editing is here preferably based on film footagespecifications to produce a cutlist for creating a final film version.

[0041] The user interface of the electronic editing system is designedto accommodate film editors concerned with any of the three filmproduction types given above. As shown in FIG. 7, the video display CRT12 of the system, which includes the source video window 36 and editedvideo window 38, displays metrics 37, 39 for tracking the position ofdigital frames in a scene sequence currently being played in the sourcewindow or the edit window. These metrics may be in either film footageformat or video time code format, whichever is preferred by the user.Thus, those film editors who prefer film footage notation may edit inthat domain, while those film editors who prefer video timecode notationmay edit in that domain. In either case, the digitized frames correspondexactly with the 24 fps speed of the original source film, rather thanthe 29.97 fps speed of videotape, so that the electronic edits producedby the electronic editing correspond exactly with the film edits, as ifthe film were being edited on an old-style flat bed editor.

[0042] As an example of an editing session, one scene could be selectedfrom the bin and played on the source window 36 of the system CRTdisplay 12. A film editor could designate frame points to be moved orcut in either timecode or film footage format. Correspondingly, audiopoints could be designated to be moved or the audio level increased (ordecreased). When it is desired to preview a video version of such edits,an NTSC video is created by the system based on the sync information inthe electronic bin, from the system disc storage, to produce either aso-called rough cut video, or a final video version. In this process,the system generates an analog version of the digital video signal andrestores the redundant video frames necessary for producing the NTSCvideo rate. The system also produces a corresponding analog audio trackand decreases the audio speed so that the audio is synchronized with thevideo. In this way, the system essentially mimics the telecine processby slowing down the video and audio and producing a 29.97 fps videotapebased on a 24 fps source.

[0043] Referring again to FIG. 1, in creating an NTSC video from adigitized film version, the video compressor 30 retrieves the digitizedvideo frames from the computer 18 and based on the electronic bininformation, designates video fields. The video A/D 26 then creates ananalog version of the video frames and processes the frames using apulldown scheme like that illustrated in FIG. 2 to introduce redundantvideo frames. The video speed is then controlled by the timing circuit28 to produce 29.97 fps video as required for an NTSC videotape.Correspondingly, the system audio process 24 and audio A/D 22 processesthe digital audio signal based-on the electronic bin to generate ananalog version of the signal, and then slows the signal by 0.1% tosynchronize the audio with the NTSC video. The final video and audiosignals are sent to the videotape recorder 20, which records the signalson a videotape.

[0044] The electronic editing system may be programmed to produce anedit listing appropriate to the particular media on which the finalizedversion of the film source material is to appear. If the source filmmaterial is to be finalized as film, the system may be specified toproduce a cut list. The cut list is a guide for conforming the filmnegative to the edited video copy of the film footage. It includes apull list and an assemble list. The assemble list provides a list ofcuts in the order in which they must be spliced together on the film.The pull list provides a reel-by-reel listing of each film cut. Each ofthese lists specifies the sync points for the cuts based on film footageand frame keycode, as if the film had been edited on a flatbed editor.If the source film material is to be finalized as video, the system maybe specified to produce an edit decision list (EDL). The EDL specifiessync points in video time code, as opposed to film footage. The editingsystem generates the requested edit lists based on the electronic bin;as the film is electronically edited, the bin reflects those edits andthus is a revised listing of sync points corresponding to the editedfilm version. Because the bin is programmed to specify sync points inboth film footage and video timecode, the editing system has directaccess to either format, and can thereby generate the requested EDL orassemble and pull lists. Appendix B consists of examples of an EDL,assemble lists, and pull lists, all produced by the electronic editingsystem. Thus, at the end of an electronic film edit, the editing systemprovides a film editor with an NTSC videotape of the film edits and aedit list for either film or videotape.

[0045] Other embodiments of the invention are within the scope of theclaims.

What is claimed is:
 1. An apparatus comprising: a random access computerreadable medium for storing a plurality of sequences of digital imagesfrom one or more sources of frames captured for playback at a rate of 24frames per second, wherein each of the sequences of digital images isstored as a data file of a file system of a computer and has imageshaving a one-to-one correspondence with the rate of 24 frames persecond; a nonlinear editing system, including: means for permitting auser to specify scenes from the sequences of digital images stored inthe data files on the random access computer readable medium, wherein ascene is defined by a reference to a data file storing a selected one ofthe sequences of digital images and by frame points designated in theselected sequence of digital images, wherein the frame points may bedesignated at any frame boundary using a metric based on the playbackrate of 24 frames per second; means for permitting a user to specify asequence of one or more specified scenes; selection means for enabling auser to select one of a plurality of output frame rates; and means forproducing a representation of an audiovisual work from the specifiedsequence of scenes in accordance with the selected one of the pluralityof output frame rates.
 2. The apparatus of claim 1, wherein one of theplurality of output formats includes video played back at a rate of29.97 frames per second.
 3. The apparatus of claim 1, wherein one of theplurality of output formats includes video played back at a rate of 24frames per second.
 4. The apparatus of claim 1, wherein one of theplurality of output formats includes film.
 5. The apparatus of claim 1,wherein one of the plurality of output formats includes video playedback at a rate of 25 frames per second.
 6. The apparatus of claim 1,further including: means for storing information about the designatedframe points of each specified scene from the specified sequence ofscenes from the sequences of digital images using a metric based on therate of 24 frames per second; and means for updating the storedinformation with the designated frame points of each specified scene inresponse to specification of the scenes from the sequence of digitalimages.
 7. The apparatus of claim 6, wherein the stored informationfurther comprises information about the designated frame points of eachof the specified scenes from the specified sequence of scenes from thesequences of digital images using a metric based on the rate of 29.97frames per second.
 8. The apparatus of claim 1, wherein therepresentation of the audiovisual work is an edit decision list.
 9. Anapparatus comprising: a random access computer readable medium forstoring a plurality of sequences of digital images from one or moresources of frames captured for playback at a rate of 24 frames persecond, wherein each of the sequences of digital images is stored as adata file of a file system of a computer and has images having aone-to-one correspondence with the rate of 24 frames per second; anonlinear editing system, including: means for permitting a user tospecify scenes from the sequences of digital images stored in the datafiles on the random access computer readable medium, wherein a scene isdefined by a reference to a data file storing a selected one of thesequences of digital images and by frame points designated in theselected sequence of digital images, wherein the frame points may bedesignated at any frame boundary using a metric based on the playbackrate of 24 frames per second; means for permitting a user to specify asequence of one or more specified scenes; means for storing informationabout the designated frame points of each specified scene from thespecified sequence of scenes from the sequences of digital images usinga metric based on the rate of 24 frames per second and a second framerate different from the rate of 24 frames per second; means for updatingthe stored information with the designated frame points of eachspecified scene in response to specification of the scenes from thesequence of digital images; and means for producing an audiovisual workusing the specified sequence of scenes in accordance with a selected oneof a plurality of output frame rates.
 10. The apparatus of claim 9,further comprising selection means for enabling a user to select theselected one of the plurality of output frame rates.
 11. The apparatusof claim 9, wherein one of the plurality of output formats includesvideo played back at a rate of 29.97 frames per second.
 12. Theapparatus of claim 9, wherein one of the plurality of output formatsincludes video played back at a rate of 24 frames per second.
 13. Theapparatus of claim 9, wherein one of the plurality of output formatsincludes film.
 14. The apparatus of claim 9, wherein one of theplurality of output formats includes video played back at a rate of 25frames per second.
 15. The apparatus of claim 9, wherein the storedinformation further comprises information about the designated framepoints of each of the specified scenes from the specified sequence ofscenes from the sequences of digital images using a metric based on therate of 29.97 frames per second.